Abstract 20287: Optimization of the Oxygen Affinity of Hemoglobin Based Oxygen Carrier (HBOC) Can Improve Myocardial Function Following Global Ischemia
Background: In approximately 70% of cardiac arrests return of spontaneous circulation is not achieved, in part due to the inadequate re-oxygenation of the ischemic myocardium during CPR. Hemoglobin based oxygen carriers (HBOC) offer a potential adjunct to improve early re-oxygenation, however the optimal oxygen affinity to enhance myocardial re-oxygenation is not known. We compared 3 different HBOC solutions, each with unique p50 (O2 tension at which hemoglobin is 50% saturated with O2) characteristics, at the onset of reperfusion of the ischemic heart. We hypothesized that early improvement of myocardial oxygen delivery would improve early myocardial recovery.
Methods: Hearts isolated from male Sprague-Dawley rats underwent 25 min of global ischemia and then were reperfused for the first 10 min with one of the pre-oxygenated HBOC's; 1) HBOCR, (polymerized bovine hemoglobin fixed in ‘relaxed’, deoxygenated state) p50 = 2.4 mm Hg, n=3, 2) HBOCT (polymerized bovine hemoglobin fixed in ‘tense’, oxygenated state) p50 = 48 mm Hg, n=6, or 3) HgbB (isolated bovine hemoglobin) p 50 = 29 mm Hg, n=4. All hearts were subsequently reperfused for 50 minutes with modified Krebs Henseleit buffer. Continuous LV function was determined. Oxygen content (CO2), oxygen delivery (DO2), and extraction ration (MVO2/CO2) were measured at 2, 5, 10, 30, and 60 minutes of reperfusion.
Results: During the first 10 minutes of reperfusion, HgbB had the highest DO2 (HgbB = 51.7 ± 7.9 (mls O2/min), HBOCT = 23.9 ± 1.9 (mls O2/min), and HBOCR = 10.6 ± 1.3 (mls O2/min), p < 0.0001 with ANOVA). Recovery of cardiac function (percent of baseline rate pressure product (RPP) and dP/dt) was similarly higher in the HgbB (HgbB recovery 45.6 ± 11.0% RPP and 58.4 ± 13.6% dP/dt, HBOCT recovery 40.7 ± 6.3% RPP and 53.3 ± 8.0% dP/dt, and HBOCR recovery 36.3 ± 6.7% RPP and 38.5 ± 7.1% dP/dt, p = 0.78, RPP and 0.47, dP/dt with ANOVA).
Conclusions: For reperfusion of the ischemic myocardium, the HBOC's oxygen affinity (p50) is a critical determinant in overall myocardial DO2. Improved early DO2 is associated with improved recovery of cardiac function.
- © 2010 by American Heart Association, Inc.